Eureka Server初始化源码解析

Eureka Server启动初始化主要是在EurekaBootStrap类中，如下：

 @Override
    public void contextInitialized(ServletContextEvent event) {
        try {
            // 初始化 Eureka-Server 配置环境
            initEurekaEnvironment();

            // 初始化 Eureka-Server 上下文
            initEurekaServerContext();

            ServletContext sc = event.getServletContext();
            sc.setAttribute(EurekaServerContext.class.getName(), serverContext);
        } catch (Throwable e) {
            logger.error("Cannot bootstrap eureka server :", e);
            throw new RuntimeException("Cannot bootstrap eureka server :", e);
        }
    }

initEurekaEnvironment()方法主要是配置Eureka Server的环境信息 Eureka Server的初始化主要在initEurekaServerContext()方法中，下面来看这个方法。

 protected void initEurekaServerContext() throws Exception {
        //读取Eureka Server配置
        EurekaServerConfig eurekaServerConfig = new DefaultEurekaServerConfig();

        // For backward compatibility
        //Eureka-Server 请求和响应的数据兼容
        JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);
        XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);

        //创建 Eureka-Server 请求和响应编解码器
        logger.info("Initializing the eureka client...");
        logger.info(eurekaServerConfig.getJsonCodecName());
        ServerCodecs serverCodecs = new DefaultServerCodecs(eurekaServerConfig);

        ApplicationInfoManager applicationInfoManager = null;

        //创建Eureka Client
        if (eurekaClient == null) {
            EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())
                    ? new CloudInstanceConfig()
                    : new MyDataCenterInstanceConfig();
            
            applicationInfoManager = new ApplicationInfoManager(
                    instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());

            //读取Eureka Client配置信息
            EurekaClientConfig eurekaClientConfig = new DefaultEurekaClientConfig();
            eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);
        } else {
            applicationInfoManager = eurekaClient.getApplicationInfoManager();
        }

        //创建注册表
        PeerAwareInstanceRegistry registry;
        if (isAws(applicationInfoManager.getInfo())) {
            registry = new AwsInstanceRegistry(
                    eurekaServerConfig,
                    eurekaClient.getEurekaClientConfig(),
                    serverCodecs,
                    eurekaClient
            );
            awsBinder = new AwsBinderDelegate(eurekaServerConfig, eurekaClient.getEurekaClientConfig(), registry, applicationInfoManager);
            awsBinder.start();
        } else {
            registry = new PeerAwareInstanceRegistryImpl(
                    eurekaServerConfig,
                    eurekaClient.getEurekaClientConfig(),
                    serverCodecs,
                    eurekaClient
            );
        }

        //创建Eureka Server集群节点集合
        PeerEurekaNodes peerEurekaNodes = getPeerEurekaNodes(
                registry,
                eurekaServerConfig,
                eurekaClient.getEurekaClientConfig(),
                serverCodecs,
                applicationInfoManager
        );

        //创建 Eureka-Server 上下文
        serverContext = new DefaultEurekaServerContext(
                eurekaServerConfig,
                serverCodecs,
                registry,
                peerEurekaNodes,
                applicationInfoManager
        );

        //初始化 EurekaServerContextHolder
        EurekaServerContextHolder.initialize(serverContext);

        //初始化 Eureka-Server 上下文
        serverContext.initialize();
        logger.info("Initialized server context");

        // Copy registry from neighboring eureka node
        //从其他 Eureka-Server 拉取注册信息
        int registryCount = registry.syncUp();
        registry.openForTraffic(applicationInfoManager, registryCount);

        // Register all monitoring statistics.
        //注册监控
        EurekaMonitors.registerAllStats();
    }

整体流程图：